Department of Zoology, St. John's College, Dr. B.A. Ambedkar University, Agra, U.P., India.
Higher incidence of diapause in larvae of Helicoverpa armigers was recorded when larvae were exposed to thermophotoperiods with cryophase of 20 to 25°C, than under thermoperiods during constant darkness. On the otherside, larvae exhibited significantly lower percentage of dispause when exposed to cryophases lower than 20°C under thermo or thermophotoperiodic conditions. Significantly shorter time was also needed for diapause development after exposure of diapausing larvae to continuous light than to continuous darkness under 35°C. Thermoperiods of different amplitudes with the same mean temperature clearly proved that the higher temperature is responsible for higher rate of diapause development inspite of the relatively low temperature.
